This invention relates to a clamp ring device for a plurality of bolt-clamp members to facilitate securing and removal of a cover over a pressure vessel, and includes an annular clamp ring having a plurality of evenly spaced coaxial through bores for the reception of cover bolts and associated cover nuts as well as for the guide of clamping pistons, the bores being sealed against the clamping pistons by the provision of high-pressure seals each having a dynamic packing ring and a static packing ring as well as a support ring between the two packing rings.
Bolt-clamp members for pressure vessel covers function the same as when provided for the securing and removal of reactor pressure vessel covers (see U.S. Pat. No. 4,216,876).
The proper functioning of sealed covers over steam generators or pressurizers largely depend upon a uniform pressure force exerted via the bolted joint from the cover on to the sealing surface. Hence, care must be exercised to assure that all the bolts are prestressed simultaneously and that each individual bolt transmits a proportional pressure force. The advantage of such bolt-clamp members is that a uniform bolt elongation is achieved by a uniformly high cylinder efficiency. Furthermore, time-consuming, strenuous and dangerous manual labor can be avoided. In addition, a considerable lessening in the time required for securing and removing the cover with reduced personnel requirements, is advantageous.
The clamp rings for bolt-clamp members used heretofore consisted of heat-treated steel since the ring itself defines a plurality of clamping cylinders for clamping pistons arranged to be axially displaceable therein. Therefore, the clamp ring material is stressed at high pressures, i.e., a pressure ranging from approximately 500 bar to its yield point.
Special problems arise when sealing cylinders at high pressure because the gap between the piston and cylinder to be sealed increases under the influence of the operating pressure due to the deformation of the elastic material.